Various polymers, swellable clays, and multi-layer articles of manufacture have been applied to the surface of soil to provide a waterproofing layer to prevent the penetration of water and hazardous or toxic materials into the earth, and to provide lagoons, ponds and other water-containment areas. Water-swellable clays, such as bentonite, have been applied directly to the soil surface and impacted in place, as disclosed in this assignee's prior U.S. Pat. No. 3,986,365. In addition, many different multi-layered articles of manufacture containing a water-swellable clay, such as bentonite, have been manufactured by adhesively securing the water-swellable clay to major interior surfaces of flexible sheet materials, e.g., Clem U.S. Pat. No. 4,501,788, for application to the soil surface in abutting or overlapping relation to adjoining multi-layered articles. Examples of other flexible sheet materials containing adhesively secured water-swellable clays are found in the following U.S. Pat. Nos. Clem 4,467,015; McGroarty, et al. 4,693,923; Harriett 4,656,062; and Harriett 4,787,780.
U.K. published Patent Application GB 2,202,185A discloses a layer of water-swellable bentonite between flexible fabric layers that have been needle punched together in a needle loom that secures the upper and lower layers together, wherein at least one of the fabric layers is a non-woven textile material.
Another waterproofing barrier, disclosed in Blais U.S. Pat. No. 4,344,722, is constructed in the field by applying a first flexible, water-permeable fabric layer, overlaying a thickness of water-swellable clay material and applying an overlay of the same flexible, water-permeable fabric thereover. Other patents disclosing the use of water-impermeable layers for protecting a soil surface include British Patent Specification 1,059,363; British Patent Specification 1,029,513 and British Patent Specification 1,129,840.
German Patent DE 37 04 503 C2 discloses an article having two fabric layers including one non-woven fabric, surrounding a bentonite clay layer wherein the two fabric layers are needle punched together. Crawford U.S. Pat. No. 4,565,468 discloses an article including two fabric layers surrounding a bentonite clay layer wherein the two fabric layers are quilted together in a pattern forming four sided compartments.
While the Blais waterproofing barrier does not require the use of adhesive because the multiple layers are assembled at their final location, this at-site assembly is disadvantageous because of the increased man hours necessary to construct the barrier at the site and because of the attendant difficulty in applying a uniform thickness of the water-swellable clay over the lower fabric layer with relatively crude construction equipment.
One of the problems associated with the manufacture of a water barrier constructed from upper and lower fabrics surrounding a layer of bentonite clay is that the intermediate clay layer can have only a limited thickness without the clay shifting or sliding during manufacture, shipping, handling and installation thereby causing the product to have different levels of water-absorbent material at different points over the surface area of the product and surface area being protected from water penetration. Further, a portion of a clay layer that is too thick will fall out from the edges of the product, even if the surrounding fabrics are tightly needle punched or otherwise secured together.
Further, prior art needle punched products require relatively thick fabric layers above and below the water-absorbent material making it difficult to form a good seal at seams or areas of overlap since very little to no water-absorbent material will extrude through the upper or lower fabric surfaces for seam sealing. Further, the prior art "layered" products that include two fabric layers and an intermediate bentonite clay layer can separate during manufacture, shipping, handling and installation.
The articles of the present invention are manufactured such that the fiber is contained essentially throughout the article and the composite article is manufactured in a single layer, having fiber contained throughout the entire thickness of the article. The article contains one or more powdered or granular materials, such as a water-absorbent material, e.g., bentonite clay, distributed throughout any portion of the fiber, during or after manufacture. The powdered or granular, e.g., water-absorbent material, is essentially immune from separation or substantial shifts and losses of water-absorbent material since the material is relatively densely surrounded by fiber, having an amount of fiber, by weight, of at least 3%, preferably at least about 5% and up to about 80% by weight fiber throughout the thickness of the article.
The clay interlocking between fibers achieved in accordance with the present invention, wherein the clay is surrounded by a relatively dense volume of intertangled horizontal fibers, and optionally may be further interlocked by needling to also provide vertically disposed fibers tangled with generally horizontally oriented fibers, thereby more securely interlocking the clay in position, is new and unexpected in the flexible water barrier art. Surprisingly, sufficient clay can be incorporated between fibers such that the resulting article performs at least as well as the prior art products that include a central layer of relatively pure bentonite clay, and having only about 0.1% to about 2% by weight vertical fibers that have been distributed through the clay-fiber matrix as a result of needling or sewing.
In accordance with one important embodiment of the present invention, a coating of a water-insoluble adhesive is applied over one or both major outer surfaces of the article of manufacture, particularly the article that is consolidated by needle punching. Surprisingly, a relatively light coating, e.g., about 0.001 gm to about 50 gm/ft.sup.2, preferably about 0.01 to about 15 gm/ft.sup.2 water-insoluble adhesive over one or both of the outer surfaces of the article increases the tensile strength of the needle-punched waterproofing articles to prevent delamination or tearing of the article, and to reduce elongation, particularly when installed on sloping terrain. In other embodiments, water-impermeable layers can be adhered to one or both exterior surfaces of the fabric to provide additional or safety layers of impermeability with or without an adhesive under the water-impermeable layer(s).
The above disadvantages of prior art "layered" clay-containing water barrier articles are overcome in accordance with the principles of the present invention, as will be described in more detail hereinafter.